Radially structured nickel-based precursor and preparation method thereof

Abstract

The present invention discloses a radially-structured nickel-based precursor and a preparation method thereof. An overall shape of the precursor is a secondary sphere formed by agglomeration of primary crystal grains; and the secondary sphere has a loose and porous network core inside and uniform and regular strip primary crystal grains outside, and the strip primary crystal grains grow outward perpendicularly to a surface of the core and are arranged radially and closely. The precursor structure of the present invention is more suitable for high-power battery cathode materials. The internal loose structure is more likely to form a void in the center during a preparation process of a cathode material, which helps to expand a contact area between an active material and an electrolyte.

1 . A radially-structured nickel-based precursor, wherein an overall shape of the precursor is a secondary sphere formed by aggregation of primary crystal grains; the secondary sphere has a loose and porous network core inside, and has a uniform and regular strip-shaped primary crystal grains outside, and the strip-shaped primary crystal grains grow outward perpendicularly to a surface of the core and are arranged radially and closely; and the precursor has a chemical formula of Ni x Co y Mn z M (1−x−y−z )(OH) 2 , wherein 0.5≤x<1, 0≤y≤0.5, 0≤z≤0.5, and M is a doping element; a diameter of the core of the precursor accounts for more than ½ of a diameter of an entire precursor particle;
 the radially-structured nickel-based precursor is prepared by the following method, comprising the following steps: 
 (1) adding a metal solution, an alkali liquor, and ammonia water to a first reactor, and heating and stirring to allow a reaction to prepare a seed crystal, during the reaction controlling the pH within a range of 9 to 12, and controlling the ammonia concentration in the at 0 to 5 g/L, and continuously feeding the metal solution, the alkali liquor, and the ammonia water until a particle size reaches a target value of the seed crystal; and 
 (2) adding the seed crystal, the metal solution, the alkali liquor, and the ammonia water to a second reactor, and heating and stirring to allow a reaction, during the reaction, controlling the pH at 9 to 12, controlling an ammonia concentration in the reaction system at 5 to 10 g/L, and continuously feeding the metal solution, the alkali liquor, and the ammonia water until a particle size reaches a target value of the precursor to obtain a product; and collecting, washing, dewatering, and drying the product to obtain the radially-structured nickel-based precursor; 
 wherein the metal solution comprises a nickel salt and one or two selected from the group consisting of a cobalt salt and a manganese salt. 
 
     
     
         2 . The radially-structured nickel-based precursor according to  claim 1 , wherein the precursor has an average particle size of 3 to 10 μm. 
     
     
         3 . The radially-structured nickel-based precursor according to  claim 1 , wherein M is one or more from the group consisting of Al, Mg, W, Zr, and Ti. 
     
     
         4 . The radially-structured nickel-based precursor according to  claim 1 , wherein total metals in the metal solution have a molar concentration of 1.0 to 2.5 mol/L. 
     
     
         5 . The radially-structured nickel-based precursor according to  claim 1 , wherein the metal solution further comprises a doped metal salt, and the doped metal salt is one or more selected from the group consisting of aluminum sulfate, aluminum nitrate, sodium aluminate, magnesium sulfate, magnesium nitrate, magnesium chloride, sodium tungstate, tungsten trioxide, zirconium sulfate, zirconium nitrate, titanium chloride, titanic acid, and titanium tetrachloride. 
     
     
         6 . The radially-structured nickel-based precursor according to  claim 1 , wherein in step (1), when the particle size reaches the target value of the seed crystal, the pH is increased to make a new crystal nucleus grow, such that a particle size of the seed crystal in the reactor can be always kept around the target value. 
     
     
         7 . The radially-structured nickel-based precursor according to  claim 1 , wherein in step (2), when the particle size reaches the target value of the precursor, the seed crystal is fed while overflowing to maintain a solid content in the reactor relatively stable, such that a particle size of the precursor in the reactor can be always kept around the target value. 
     
     
         8 . The radially-structured nickel-based precursor according to  claim 1 , wherein in steps (1) and/or (2), the heating is conducted at 50-80° C.